They'd absolutely force a direct crit heal for that ability, just to make sure the healing was ridiculous on single target as well.
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Team member logged the fun Tender Valley run I had and it turns out I'm good with mitigation healers:
https://i.imgur.com/3l47QkO.png
The DPS was rather high, last boss got record quick meltdown. WHM pretty sure had zero hardcast heals, million holys. During that run I did hit a lot of party mitigation/regen timings (with mix of job/uncapped tome gear so low).
Another run, more typical with some screw ups, benes:
https://i.imgur.com/6kPGn5g.png
I had a run as a Warrior with a friend who was on Sage through one of the Expert dungeons. I specifically asked them to not directly heal me at all, ever, and furthermore I would purposefully click off any AoE buffs I picked up.
Still didn't even come close to breaking a sweat. Pop bloodwhetting on CD and maybe a couple other things in between and good to go. And my WAR is only 697
I believe Yoshi P said something about making the game slightly harder. I believe a WAR that can completely self heal without proper mitigation in a dungeon might be slightly brain dead. (Along with the shortest world first savage race in the games history. Lol harder btw)
At least they have the attention seeking part of being a WAR main down.